The prior art already describes various devices and methods for selectively destroying cells inside a living subject's body, in particular a mammal, including a human being. For example, U.S. Pat. No. 2,559,227 to RIEBER describes a shockwave-generating device for destroying cells inside a human body, using a truncated ellipsoid hermetically sealed by a membrane. The power needed for destroying the cells with this apparatus is relatively high, which is undesirable because of the existing risk of destroying sound cells.
Various other diagnosis methods have also been used for many years, for carrying out a non-invasive detection of pulmonary hypertension or the presence of tumors. TICKNER et al. for example, in their article "Non-invasive Assessment of Pulmonary Hypertension using Bubble UTS Resonance Pressure (BURP) Method", Nat. Tech. Inf. Service Rept. No. HR-62917-1A, April 1977, and also U.S. Pat. No. 4,265,251, have described a diagnosis method using the injection, in the blood vessels, of gas bubbles or of gas bubble precursor, in order to determine the blood pressure with the help of an ultrasonic apparatus, and the blood flow and to deduce therefrom the information which will reveal the presence or absence of heart or pulmonary disorders. U.S. Pat. No. 4,316,391 describes the use of a bubbles-precursor solid material in microcapsules encapsulating a gas of selected composition, the microcapsules having a diameter ranging between 0.5 and 300 .mu.m. Document EP-A-0 072 330 describes improvements in the ultrasonic detection system using ultrasonic frequencies for generating fine bubbles in situ which bubbles are thereafter detected by monitoring the Doppler effect. Patents DE-A-29 46 662 and EP-A-0 273 140 describe the same teaching.
Document WO-A-80/02365 to RAZOR likewise uses the injection of microbubbles of gas having diameters in the 0.5 to 300 .mu.m range, for detecting tumors as well as for delivering gaseous therapeutic agents selectively to tumors, as indicated in page 4, lines 4 to 9 and 14 to 30, and also in the claims.
It is clear from the foregoing that the prior art uses the gas bubbles essentially, if not solely, for diagnosis purposes, and in particular for measuring blood pressure. Only in document WO-A-80/02365 is there a possibility of selectively feeding gaseous therapeutic agents to tumors for treating them. This last solution is, on the other hand, hardly usable since the number of therapeutic agents which can be delivered in gaseous form and which are also capable of treating a given tumor, is extremely reduced so that this method of treating tumors by a gaseous therapeutic agent has not found an outlet in therapeutic practice.